Art of lead pencil manufacture



Nov. 9, w37. K. M. HERsTl-:IN 2,098,452

ART OF LEAD PENCIL MANUFACTURE Filed Jan, 31, 1956 INVENTOR Karl MHe/zse'fa I BY ATTORNEYS =A nted Nov. 9, 1937 ART oF LEAD PENCIL MANUFCTURE Karl M. Herstein, New York, N. Y., asslgnor to. Eagle Pencil Company, New York, N. Y., a corporation oi Delaware Application January 31, 1936, Serial No. 61,639

12 claims. `(ci. 12o-s3) My present invention relates more especially to the art of making pencils of the conventional type and has the same general objects -as those of the prior patent to Gonzalez No. 1,892,508 of De- 5 cember 27, 1932.

It is among the more specific objects of the invention, to accomplish, without the use of strongly caustic materials and in fact without the use of either acids or .bases the/eiiective bond l of the greased lead surface with the Water soluble glue by which the lead is to be affixed within the wooden case, and to accomplish amechanical keying eiect of the lead into the case in addition to the adhesive action of the glue.

` 15 The invention considered from various aspects embraces the method of 'fabricating boththe lead and the pencil as well as the resultantnovel structures as such.

In the accompanying drawing in which is 20 shown one of various possible embodiments of the several features of the invention,

Fig. l is a disassembled view showing a pencil lead about to be assembled in its case,

Fig. 2 is an enlarged .transverseI sectional view through the completely assembled pencil, and

Fig. 3 is a greatly enlarged cross sectional view showing the novel bond aorded by the glue between the lead and the case.

Referring now to the drawing, Figs. l and 2 30 show in general outline the conventional lead pencil iii-which numeral lll designates the lead and the numerals il, the two conventional 'half sections of the wooden case, which are bonded to each other at the contacting faces and to and about the lead, by a layer of interposed glue, preferably double fish glue.

Leads or other marking rods which are formed by extruding through dies, usually include various greasy or oily materials such as tallow, stearic acid or the like, in varying proportions according to the nature or kind of mark for which the pencil is designed. These leads of conventionalV construction are, according to the present invention, coated with crystals oi a detergent salt or salts that have bitten into and are securely bonded to the greasy surface of the lead from which they also protrude to aord a non-greasy anchorage for the glue.

50 The crystals are preferably aixed to the leads by applying an aqueous solution oi the salt thereto and this preferably by immersing the leads into the solution, although the solution may he sprayed or otherwise applied to the leads. The

55 leads may thereupon be dried in any appropriate fil manner, as by storing them in a warm dry chamber but preferably by centrifuging them.

The .crystals forming, as the water solvent "is removed from the exterior, by virtue of the detergent character of the salt bite into and combine 5 with the grease exposed at the surface of the lead and accordingly become bonded thereto by a -combined physical and chemical action. When the free water has been removed, a considerable 'portion of the crystal mass will be found to prol() trude outward from the lead, beyond the greasy surface thereof. When the lead is dry, it therefore presents a generally whitish appearance and is rough to the touch, due to the protruding crystal lengths.

After the lead thus formed and treated has dried it can be incorporated within the pencil in the usual manner by coating the sections I l with the glue, depositing the lead along the groove of one of said wood sections, superposing the other thereon and applying mechanical pressure thereto to cause the glue to bond the elements together. As suggested by Fig. 3, the glue l5 which readily becomes bonded to the surface of the wood takes an adequate hold upon the exposed faces i3 of the detergent salt crystals, which in turn, asi previously described, bite into and securely grip the greased surface of the lead at Hi. Thus there is a mechanical keying bond of the crystals to the lead on the one hand and to the glue onl the other, and this, in' addition to the adhesive bond. While the process admits of a wide variety of modiiications one illustrative, specific, practical procedure for carrying the same into execution is '35 to immerse the leads in saturated solutions of anyappropriate detergent salt or mixture of salts. Among the salts that have the required property of being detergent and of crystallirzing readily are tri-sodium phosphate, sodium meta-silicate, so- 40 dium carbonate and borax.

After immersion for a period of time varying from a half hour to three or four hours, according tc the salt selected, the leads are withdrawn from -the solution, centrifuged to remove the bulk of solution, and the remainder which is adherent to the leads is dried in a warm chamber for a few hours or overnight.

Bearing in mind that the crystal salts described are for the most part highly soluble in water, 5o they will taire on water irom the glue before the latter is dry which contributes to a further growth and to amore secure adhesive and mechanical keying bond with respect to the gluf. than would otherwise be the case. The crystalline structure thereby engendered isjsumciently soft in nowise to interfere with the sharpening of the pencils. p

It will of course be possible by varying the condition of concentration ofthe salt and the temperature of th' solution to modify the treatment so as to control the character of the crystalline structure formed and the type or effectiveness of bond produced.

It will thusbe seen that there is herein described an article and a method in which the several features of this invention are embodied, and which article and method in their action attain the various objects of the invention and are well suited to meet the requirements of practical use.

As many changes could be made in the embodiments disclosed, and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What I claim as new and desire to secure by Letters Patent is:-

l. The processing of pencil leads which includes the application to the greasy surface of the lead, of a solution of a grease-attacking crystalline salt and evaporating such solution, with resultant crystals in part penetrating the greased lead surface and in part protruding therefrom.

2. The method of producing a lead pencil which .includes the step of applying to the greasy surface of the'lead a solution ofgrease attacking crystalline salt and evaporating such solution, with resultant crystals, in part penetrating the greased lead surface and in part protruding therefrom and gluing the lead within the case, whereby the lead will become anchored in place by the keying of the crystals. protruding in part into the greasy surface of the lead and in part into the glue.

3. In the art oi' pencil lead manufacture, the

step of immersing the usual greasy leads in a solution of a grease attacking detergent salt that will crystallize upon drying.

4. In the art of lead pencil manufacture, the process of immersing the usual greasy leads in a solution of grease attacking detergent salt that wilrcrystallize upon drying, then drying the leads and gluing them within the pencil case.

5. In the art of pencil lead manufacture, the step of immersing the usual greasy leads in a solution of grease attacking detergent salt of sodium that will crystailize upon drying.

. 6. In the art of pencil lead manufacture, the step of immersing the usual greasy leads in a solution of grease attacking detergent salt of the group whichconsists of tri-sodium phosphate, sodium meta-silicate, sodium carbonate and yborax and permitting the salt to crystalline upon the lead.

'7. In the art of pencil lead manufacture, the step of immersing the usual greasy leads in a grease attacking solution of the salt tri-sodium phosphate and permitting the salt to crystallize upon the lead.

8. In the art of pencil lead manufacture, the step of immersing the usual greasy leads in a grease attacking solution of the salt sodium metasiiicate and permitting the salt to crystallize upon4 surface of the lead and protruding outward therefrom, a layer of glue covering the protruding crystal segments and bonded thereto and a pencil case aboutA said glue and adhesively bonded thereto.

12. A lead pencil comprising alead, crystals of a detergent and highly soluble salt penetrating the outer greasy surface of the lead and protruding outward therefrom, a layer of glue covering the protruding crystal segments, some of the water of said glue being incorporated in said crystals for more adequate bond of the crystals with respect to the glue and a pencil case about said glue and adhesively bonded thereto.

` l KARL M. HERS'I'EIN. 

